Presently, a common temporary storage device always uses mechanisms such as rollers and a rolling belt. The storage device includes a storage roller driven by a first drive motor, a belt standby roller driven by a second drive motor and a coiling belt with two ends fixed on the storage roller and the belt standby roller respectively, which is wound around, and is retracted and deployed between the storage roller and the belt standby roller. The first drive motor and the second drive motor are controlled to be started or stopped by a micro controller. This temporary storage device operates in a way that the rollers cooperates with the coiling belt to implement temporary storage of a banknote.
During operation of the temporary storage device, to ensure equally spaced banknotes, it is required to ensure that speeds of different portions of the coiling belt are constant and consistent while the coiling belt is constantly tightened to improve the tenseness of the coiling belt, whereby the storage capacity of the storage roller is improved. According to a principle of circular motion, a linear speed v is equal to an angular speed ω times a radius r. To keep a constant banknote delivering speed, i.e., to keep the linear speeds of the storage roller and the belt standby roller constant, as the coiling belt is deployed and retracted between the storage roller and the belt standby roller, radiuses of the storage roller and the belt standby roller continually change, therefore angular speeds of the first motor and the second motor need to be adjusted timely according to the radiuses of the storage roller and the belt standby roller.
In a conventional method for controlling the temporary storage module, the radius increment ΔX of the storage roller is commonly estimated by using empirical values. The angular speeds of the first motor and the second motor are continuously adjusted according to the estimated radius increment ΔX of the storage roller and the determined radius increment ΔY of the belt standby roller, thereby ensuring that both linear speeds of the storage roller and the belt standby roller are constant and consistent. The radius change ΔX of the storage roller is an estimated value, and the radius change ΔY of the belt standby roller is a determined value setting according to the empirical values, therefore the existing method does not have enough accuracy, so that there is a difference between the linear speed of the storage roller and that of the belt standby roller, which causes loose of the coiling belt and even a cast of the coiling belt.
Besides, the radius of the storage roller is also affected by the thickness of the stored banknote, thus a real-time radius of the storage roller can not be estimated accurately in the conventional technology, and therefore, an accurate angular speed can not be accurately calculated, which can not ensure a constant linear speed of the storage roller. In a case the linear speed of the storage roller has a big difference from that of the belt standby reel, it is apt to cause the following problems: 1, unequal spaces between banknotes on the storage roller, which causes a waste of the coiling belt, reduces the storage capacity of the storage roller, and can not satisfy a design requirement; and 2, loose of the coiling belt and even cast of the coiling belt, which increases a maintenance cost.